Gentamicin, Random

GENTAR

Garamycin

Serum (gold top) tube

0.5 mL

Lithium Heparin Plasma (green top) tube or EDTA Plasma (purple top tube)

Serum (gold top) tube, Lithium Heparin Plasma (green top) tube or EDTA Plasma (purple top) Tube

Room Temperature or Refrigeration

Room Temperature - 2 hours; Refrigerated - 7 days

Hemolysis, Quantity Not Sufficient, IV contamination

Daily upon receipt

Upon completion of analysis

Concentrations of β-lactam antibiotics (penicillins and cephalosporins) at therapeutic levels may inactivate gentamicin in vivo and in vitro. Specimens from patients receiving β-lactam antibiotics (penicillins and cephalosporins) must be analyzed immediately upon collection or stored frozen to prevent in vitro inactivation of gentamicin. Trimethoprim at a concentration of 25 μg/mL (86 μmol/L) resulted in a positive bias of 0.57 μg/mL (1.2 μmol/L) at a gentamicin concentration of 5 μg/mL (10.8 μmol/L). Results for samples from patients receiving netilimicin or sisomicin, aminoglycosides structurally related to gentamicin, may be falsely elevated due to cross-reactivity in this assay (netilimicin, approximately 6% and sisomicin, approximately 7%).

No reference range listed for random gentamicin determination.

Gentamicin is used in the treatment of serious infections caused by susceptible strains of gram-negative microorganisms and particular gram-positive organisms that are resistant to less toxic antibiotics.  Gentamicin is safe and effective only in a narrow range of concentrations for a given indication.  Exposure to high gentamicin concentrations for a prolonged period may cause renal impairment or ototoxicity.  Serum or plasma gentamicin measurements are used in the diagnosis and treatment of gentamicin overdose and in monitoring levels of gentamicin to ensure appropriate therapy.